Varities of glycosyltransferases with strict specificty are involved in synthesis of glyclipids and glycoproteins in blood group ABO, P and I systems. Two human glycosytransferases, i.e., a GalNAc transferase (A-enzyme), which synthesizes the blood group A substances, and a Gal transferase (B-enzyme), which produces the B substances, were first purified to homogeneity. Using rabbit's antibody against purified A-enzyme, and examining the kinetic characteristics and membrane components associated with the blood group substances, allelism of ABO locus and underlying mechanism of several unusual blood group expressions, such as CisAB, Bm and A intermediate, have been elucidated. The aims of the renewal project are: 1) Study of genetic mechanism of abnormal expressions of blood group ABO system by exam ining molecular, kinetic and immunological properties of blood group A- and B-enzymes, and by analysis of red cell membrane components associated with the blood group substances; 2) Isolation and characterization of Alpha (1 greater than 2) Fuc transferase (or transferases), which synthesizes the H-substances, from human plasma, milk and submaxillary glands. The study will contribute towards distinguising whether the Se gene is a regulatory gene or a structural gene; and 3) Isolation and characterization of glucosyltransferases in the blood group P system, and study of genetically controlled expression of these transferases in subjects with phenotypes P1, P2 P1K, P2K, and p. The study may clarify the genetically controlled synthetic pathway of the blood group P substances.